Such a pump aggregate A (FIGS. 1 and 2) is manufactured and distributed by the applicant and is used for installation, for example, in portable tool assemblies, e.g., torque screwdrivers for generating high tightening torques. Such tool assemblies are used in the assembly of wind turbines, whereby in one model with a single-phase alternating current oil-immersed motor 7 that does not start up against pressure, a pressure shunting switch DW is contained in a valve combination V on the exterior of the housing. The pressure shunting switch can be dispensed with in aggregate models (not shown) containing a three-phase alternating current oil-immersed motor that does start up against pressure. The housing, which is frequently installed in a recumbent operating position, consists of an externally ribbed pipe section 1, housing covers 2, 4 mounted thereupon, and an optionally provided cooling fan 3 on one housing cover 2. The housing has (FIG. 2) two separated pressure outlets (pressures P1 and P3 of the pumps 5, 6) for the discharge flows discharged outwards, to which two connection ports of the valve combination are connected. In the valve combination are contained a pressure line to a pressure outlet (pressure P) of the valve combination, a return line 9 to a return connection point 8 of the housing and at least one pilot line extending to the closing control side of the pressure shunting switch DW, all formed as channels penetrating a plurality of blocks. In addition to a system pressure-limiting valve DB, the valve combination V contains a low-pressure change-over valve U to the return line 9, a check valve R, optionally the pressure shunting switch DW with an assigned aperture B and optionally a secondary pressure-limiting valve SD. At least one directional control valve W is arranged on the block group of the valve combination V. From this layout, a relatively large weight results for a particular performance specification of the pump aggregate, which fundamentally, and especially for the portable tool assembly into which the pump aggregate is to be installed, represents a considerable disadvantage. Furthermore unfavourable is the relatively high and expansive dimension of the valve combination and the directional control valve on the housing exterior that, due to vibrations caused by operation, leads to significant local stress for the housing at those locations of the two pressure outlets at which the valve combination is mounted to the housing exterior wall.
A similar pump aggregate with a dual-circuit pump system is known from EP 2 330 304 A. Here again, the valve combination is mounted on the exterior of the housing.
Further state of the art is contained in EP 2 241 753 A and EP 1 731 762 A.